An agricultural seeding machine such as a row crop planter or grain drill places seeds at a desired depth within a plurality of parallel seed trenches formed in soil. In the case of a row crop planter, a plurality of row crop units are typically ground driven using wheels, shafts, sprockets, transfer cases, chains and the like. Each row crop unit has a frame which is movably coupled with a tool bar. The frame may carry a main seed hopper, herbicide hopper and insecticide hopper. If a herbicide and insecticide are used, the metering mechanisms associated with dispensing the granular product into the seed trench are relatively simple. On the other hand, the mechanisms necessary to properly meter the seeds, and dispense the seeds at predetermined relative locations within the seed trench are relatively complicated.
The mechanisms associated with metering and placing the seeds generally can be divided into a seed metering system and a seed placement system which are in series communication with each other. The seed metering system receives the seeds in a bulk manner from the seed hopper carried by the frame. Different types of seed metering systems may be used, such as seed plates, finger plates and seed disks. In the case of a seed disk metering system a seed disk is formed with a plurality of seed cells spaced about the periphery of the disk. Seeds are moved into the seed cells with one or more seeds in each seed cell depending upon the size and configuration of the seed cell. A vacuum or positive pressure air differential may be used in conjunction with the seed disk to assist in movement of the seeds into the seed cell. The seeds are singulated and discharged at a predetermined rate to the seed placement system.
The seed placement system may be categorized as a gravity drop system or a power drop system. In the case of the gravity drop system, a seed tube has an inlet end which is positioned below the seed metering system. The singulated seeds from the seed metering system merely drop into the seed tube and fall via gravitational force from a discharge end thereof into the seed trench. The seed tube may have a rearward curvature which reduces bouncing of the seed as it strikes the bottom of the seed trench.
Seed metering systems as described above are generally effective for seed singulation and seed spacing control. However, certain operating conditions such as side hills, etc. adversely affect the seed singulation and seed spacing. The seed pool area within the seed meter is at the bottom of the meter, and the rotating seed disc lies along side the seed pool. When the seeds shift laterally away from the seed disc during a side hill condition, seed singulation and/or seed skip problems can occur resulting in undesirable seed spacing in the seed trench formed in the soil.
What is needed in the art is a seeding machine with a seed metering system that provides good seed singulation and seed spacing during a wide range of operating conditions.